Sir - The article "Telstar 4 mystery delays Asiasat 2" (Flight International, 11-17 January, P18) confirms a story which I published in Worldwide Satellite Launches on 10 October 1994. I said: "...US Spacecom has only tracked one object from the launch (1994-058A/23249) which has been nominally assigned to the satellite: however, if the satellite did disintegrate then it would be reasonable if the tracked object were to be the intact Ariane third stage..."
Turning to the DFH-3 1 mission ("China's DFH struggles into GEO"), this satellite has been abandoned by the Chinese. After a successful launch on 29 November 1994, the satellite was manoeuvred from its initial geosynchronous-transfer orbit at 28.5¡ to the equator, to an intermediate one at 12.4¡, 6,390-36,065km by mid-December. It is unclear whether this was a planned intermediate orbit, or whether the satellite's apogee engine shut down before the manoeuvre was complete.
The DFH-3 1 remained in this orbit until the end of December, while the Chinese tried to sort out what they described as a faulty navigation system, resulting in the unplanned use of attitude-control propellant. By 29 December, the satellite had been boosted to a geosynchronous drift orbit: 0.3¡, 35,180-35,990km, with a period of 1,426min, compared with a required 1,436min for a truly "stationary" orbit. By this time, the satellite was drifting away from its planned operating longitude and either the malfunction re-appeared or the satellite did not have sufficient propellant for further manoeuvres, causing the satellite to be abandoned about a week later.
While space-insurance markets might worry about the losses of the Telstar 402 and DFH-3 1, in each case the launch vehicles performed perfectly and it was the satellites, which malfunctioned.
PHILLIP CLARK
Compiler
Worldwide Satellite Launches
Molniya Space Consultancy
Heston, Middlesex, UK
Source: Flight International
